Fuel combustion



March 15, 1938. DALEN 2,111,141

FUEL COMBUSTION Filed Oct. 30, 1933 3 Sheets-Sheet l I I I I 11 INVENTOR I ATI'ORNEY March 15, 1938. G. DALEN FUEL COMBUSTION Filed Oct. 30, 1933 3 Sheets-Sheet 2 INVENTOR W .9

-J mwromuw 1161151938. G ALE 2,111,141

FUEL COMBUSTION Filed Oct. 30, 1933 3 Sheets-Sheet 3 INVENTOR W ATTORNEY Patented Mar. 15, 1938 UNITED STATES PATENT orifice FUEL COMBUSTION Application October 30; 1933, Serial No. 695,882

' In Sweden November 3, 1932 19 Claims.

The present invention relates to combustion and has particular reference to the combustion of liquid hydrocarbon fuels. Still more particularly, the invention relates to the combustion of heavy hydrocarbons,.such, for example, as what is commonly termed fuel oil.

In one of its phases, the invention relates to cook stoves, particularly stoves of the type adapted to be continuously maintained at elevated temperature. The invention, however, is not limited to such apparatus, but may also be applied to other heatconsuming devices, such as water heaters, rtefrigeration apparatus of the absorption type requiring heat for operation, and other devices having like heat requirements.

The general object of the invention is to provide for reliable continuous operation of com bustion apparatus in which heavy hydrocarbon fuel is vaporized to provide the fuel vapor necessary for combustion. Otherand more detailed objects and the nature and advantages of the invention will appear more fully in the following specification, in which'theinvention is described in its application to' a domestic cook-stove. In the drawings forming a part of the specification;

Fig. 1 is a vertical section of a domestic cookill stove taken on the line l-l of Fig. 5, including apparatus embodying the invention; Fig. 2 is a similar section on an enlarged scale showing part of the apparatus illustrated in Fig. l;

Fig. 3 is'a section taken on the line 3-3 of Fig. 2; p

Fig. 4 is a section taken on the line 4-4. of s- Fig. 5 is asection on an enlarged scale taken on the line 5-5 of Figs. 1 and 2; and Fig. 6 is a view taken on line 6-45 of Fig. 2.

Referring now to Figs. 1 and 2, the stove indicatecl generally at A is of the type adapted to be continuously maintained at elevatedtemperature and comprises a relatively heavy metal structure indicated generally at l 0 providing hot plates 12 and i4 and an oven IS. A second low temperature oven I8 may also be provided. The hot plates l2 and i4 and also oven 16 are adapted to be heated by conduction of heat through the metal from gases of combustion which pass through channel 20 to a suitable stack opening 22 adapted to be connected to the chimney. The

metal structure lll is adapted to accumulate heat and is surrounded by suitable'insulating material, such as asbestos or .kieselguhr, indicated at 24, and the hot plates l2 and Hare covered when not in use by insulated cover plates 26 and 28.

The hot combustion gases for heating the structure. iii are provided by a burner indicated generally at 30 and adapted to burn a gaseous fuel mixture comprising air and hydrocarbon fuel vapor.. Air for combustion is supplied to burner 36 through the passage 32 which is in communication with the surrounding atmosphere through the opening 34. Around the base of the burner 30 there is provided a metal mass 36 having two vaporizing chambers 38 and 40 therein (see Figs. 3 and 4). Chambers 38 and 40 are each in communication with the lower portion of the burner "ill by way of passage 42 with which the upper portions of the vaporizing chambers are in communication by way-of ports 44 and 46. Chamber 38 has associated therewith a liquid fuel feeding member #8, the lower portion of which provides a central fuel feeding tip from which liquid fuelis adapted to fall onto a vaporizing surface 52, which in this instance is provided by the bottom wall of the vaporizing chamber. The vaporizing chamber and the lower part of the fuel feeding member are connected by means of a pipe 54 and an annular space 56 communicating with pipe 54 surrounds the fuel feeding tip 50 of the member 48. Chamber 40 has asso-. ciated therewith .a like fuel feeding member 58 having a fuel feeding tip 60 adapted to cause fuel to fall onto the vaporizing surface 62. Chamher 40 and member 58 are connected by pipe 64, and tip 60 is surrounded by annular space 66.

Fuel is supplied alternatively to one or the other of the fuel feeding members by apparatus which will now be described. Liquid hydrocarbon fuel is fed, preferably by'gravity, from a suitable reservoir (not shown) through the supply line 58 (Fig. 5) through a strainer 10 in a chamber 12, from which it flows through the passage 14 to a. float chamber 16 in which the level of fluid is maintained substantially constant-by the float 18, which operates to control flow of fuel through the passage 14. From the float chamber 16 fuel flows through the pipe 80, the labyrinth 82 and pipe 84 to a feeding orifice 86 controlled by a needle valve 88. The orifice 86 is positioned above a cup-shaped receptacle an in which is pivotally mounted a plate 92 adapted to direct fuel either to the outlet passage 94 leading from chamber 98 in receptacle 90, or to the outlet passage 96 leading from chamber I00 therein. Chambers 98 and Hill are separated by the web I02. Passages and 9B communicate respectively with the fuel feeding members 58 and 48, the'connection between passage 94 and fuel feeding member 58 being shown in Fig. 2

and comprising an inclined conduit I04.

The fuel feeding members 48 and 58 and the receptacle are preferably formed by a single integral casting, as shown in Fig. 2, through which the several fuel feeding passages are bored.

The annular spaces 56 and 66 surrounding the tips of each of the fuel feeding members are placed in communication with the surrounding atmosphere to permit a restricted amount of air to be admitted at these places for a purpose to be explained later. In Fig. 2 the connection for this air supply to the fuelfeeding member 58 is shown at I06.

The lower part of the passage 42 is preferably provided with an overflow pipe indicated at I08, the outer end of this pipe terminating in a passage or discharge opening IIO (Fig. 5), beneath which there is advantageously suspended an overflow receptacle II2. Receptacle H2 is supended from a bar II4, to which is attached stem II6 of the needle valve 88, and, as will be evident from Fig. 5, flow of fuel through the orifice 86 will be shut off in the event liquid fuel overflows into the receptacle H2. The metal bar or strip H4 is supported intermediate its ends by the pivot I I8and the end of the strip opposite the end to which the needle valve stem is secured, is fastened to oneend of a hollow curved expansion element I20 of the Bourdon tube type, the other end of which is secured, as at I22, to one arm of a lever I24 pivoted at I26. The expansion element I20 is in communication with a thermostat tube I28 leading from a thermostat (not shown) and adapted to reflect the temperature of the structure I0. Tube I28 and the element I20 are adapted to be filled with any suitable expansible thermostat fluid. The fixed point of the expansible element I20 is determined by the position of lever I24, which is biased by a spring I30, working against any suitable fixed abutment I32, toward an adjustable cam I34 adapted to be rotated to determine the position of adjustment of the lever.

The position of the plate 92 for directing fuel either to passage 04 or to passage 86 iscontrolled by means of an arm I36 projecting upwardly from the plate and at its upper end engaging the bifurcated lower end I36 of a lever I40 pivoted at I42. The upper arm of lever I40 is bent so as to project through an arcuate slot I44 in the outer casing I46 of the stove, and terminates in an indicator arm 148 having an actuating handle I50. The outer casing 846 of the stove preferably has marked thereon the. scale or index'1-l5, l51, as indicated in Fig. 6.

The metal mass 36 is preferably enclosed in insulating material indicated at I52, and air passing to the air supply pipe 32 of the burner also advantageously circulates in the space I 54 around the insulation I52 and also around the fuel feeding members and the parts providing'the channels for supplying fuel and air to these members.

lNhile the form of fuel burner employed constitues per se no part of the present invention,

the burner arrangement shown herein by way of example, which forms the claimed subject matter of my copending application Serial No. 695,883, filed October 30, 1933, is of advantageous form. In this burner arrangement the metal mass 36 provides a cup-shaped space with the bottom of which passage 42 is in communication, and in the center of which there is disposed the perforated burner pipe I56. A second and larger perforated burner pipe I50, the-lower end of which is above the lower end of pipe I56, surrounds pipe I56 to provide between the two pipes an annular space I60. A third pipe I62, larger in diameter than pipe I58 and imperforate, surrounds pipe I58. The lower end of pipe I62 is above the lower end of pipe I58. The space I 60 between pipes I56 and I58 is in communication with the pipe I64, which serves to place the burner in communication with the combustion gas channel in the structure III.

The operation is as follows:

Fuel vapor is burned in the space I60 by combustion air admitted thereto through perforated pipes I56 and I58, both of which pipes are in communication with the air space I54. The heat of combustion heats the mass 36 to high temperature, a high temperature of this mass being readily maintained because of the fact that the mass is well insulated, and by conduction through the metal the vaporizing surfaces 52 and 62 are maintained at very high temperature, for example, 900 F, or higher. Liquid fuel drops or falls through the orifice 86 onto the plate 92 and flows through the associated fuel conduit to one of the fuel feeding members. From the tip of the fuel feeding member the fuel falls onto the hot vaporizing surface and is substantially instantaneously vaporized. The vapor formed in the vaporizing chamber is drawn by the draft created by the burner through the passage 42 to the space between the two perforated burner pipes. Due to the suction created by the burner draft, air is drawn through'the pipes (one of which is shown at I 06 in Fig. 2) to the spaces around the fuel feeding tips 50 and 60 of the two fuel feeding members, this admission of air being continuous with respect to both of the fuel feeding members since both of the vaporizing chambers are in uninterrupted communication with the burner and therefore are continuously subject to draft from the burner whenever the burner is in operation. The quantity of air admitted around the fuel feeding orifice is restricted, being insufficient in amount to form-a combustible gas mixture with thefuel vapors being formed in the vaporizing chamber to which fuel is being admitted. As will be evident, theair admitted through a pipe such as nine I06 will be relatively cool as compared with the temperature of the mass 36 and the parts associated therewith, and the purpose of this air supply is to enshroud the falling fuel so as to prevent premature vaporization thereof. By so enshrouding the falling fuel and conducting it to the fuel feeding member through passages which are relatively cool, the formation of carbon deposits at or adjacent to the fuel feeding member due either to premature vaporization or recondensation of fuel vapors on the wall surfaces is materially retarded if not entirely eliminated, and the formation of a carbonaceous deposit of a coke-like nature on the vaporizing surfaces is also retarded because of the fact that the oxygen content of the restrictedquantity of air, while insufficient to form a combustible gas mixture in the vaporizing chamber, will tend to burn away such carbonaceous deposit as it forms. Due to the introduction of this restricted air supply to the vaporizing chamber, the accumulation of carbonaceous deposits of fuel residue in the chamber is very slow, but in time sufficient accumulation may occur to adversely affect the efficient operation of the vaporizer, particularly when a substantial accumulation of residue or coke forms on the vaporizing surface.

In order to permit the continuous operation of.

rality of vaporizers is provided and after one vaporizer has been in operation fora period of time,

which experience has indicated will result in the accumulation of an undesirable amount of residue in the vaporizing chamber, the supply offuel to such vaporizer is cut off, and fuel is directed to another vaporizing chamber. It will be evident that in a construction such as that disclosed, fuel vapor will be substantially immediately formed in the vaporizing chamber to which fuel has been directed, so that there will beno interruption in the supply of fuel vapor to the burner. Even if there were sufficient interruption" in the supply offuel vapor to cause the burner flame to be extinguished, the entire apparatus is at such high temperature that ignition would automatically occur-immediately upon the resumption of the supplying of fuel vapor. The restricted supply of air admitted to the vaporizing chamber from which fuel has been cutoil continues to flow through this chamber under the influence of I the burner draft, and because of thefact that the vaporizing chamber is continuously maintained at very high temperaturethe oxygen in the air continuing to flow to the vaporizing chamber combines with the carbonaceous residue therein and gradually burns away the deposits in the chamber while another vaporizing chamber is in operation.

Wlth a fuel vaporizing arrangement of the kind shown, the formation of carbonaceous deposits in the vaporizing chambers is so slow that continuous operation of the burner may readily beefiected with but two vaporizing chambers adapted to be operated in alternation. ,Experi ence has shownthat where the apparatus is utilized in connection with the heating of a. cookstove of the type illustrated, vaporization of the required amount of fuel may be effected continuously by a single vaporizer fora period of about a month, but it is preferable to change operation of the Vaporizers somewhat more frequently, and in order to insure the shifting of operation of the Vaporizers-at proper intervals, the-index indicatedin Fig. 6 is advantageously employed in conjunction with the shifting lever I48.

index is advantageously marked 1-15 and1t'i- 1,

the figures representing the days of amonth, it being intended .that the shifting lever I48 be in the position shown in Fig. 6 during the period from the first to the flfteenth day of a given month, and in the opposite position during the period from the fifteenth of a given month to the first of the succeeding month. y

In the embodiment of the inventionv hereinbefore described by way ofillustration, air is employed as the'enshrouding fluid for the fuel falling onto the vaporizing surfaces, butfit will be evident that other oxygen containing fluids may be employed in accordance with theinvena The essential characteristic is that the,

tion. enshrouding fluid contain oxygen which is admitted to the vaporizing chambers at a' rate such that the enshrouding fluid is essentially inactive to produce a combustible gas mixture in the va porizing chambers, and is active only to 'the' extent of effecting the burning away of carbonaceous deposits in .these' chambers.

It will be evident that the invention'is not restricted to theuse .of but two Vaporizers, since a larger number of Vaporizers, to which fuel is alternatively supplied,.may be used, and it will further be evident that many changes and variations in the specific structure employed may be 5. Liquid fuel vaporizing apparatus for 'resorted' 'to without departing from :the spirit and scope of the invention as'deflned in the appended claims, which are to be construed as broadly as is consistent with the stateof theprior: art.

What Iclaimis: Y 1. Liquid fuelcombustion apparatus comprising a burner, a plurality of Vaporizers each including a fuel vaporizing surface and a fuel feeding member forcausing liquid fuel to fall on said ,aburr'ier, a pli irality of v'aporlzers in heat receiving relation with respect to said burner each of said [Vaporizers including a main vaporizing chamber, a vaporizing surface in said chamber continuously heatedby heat from said burner and a fuel feeding member for causing fuel to fall on "said vaporizing surface,-.- passages providing constant communication between said chambers and said burner, means for continuously admitting a gaseous combustion supporting medium to said burner, means for continuously. admitting to each' of' said vaporizing'chambers a quantity of gaseous combustion supportingmedium insu'fli cient to form a combustible gas mixture with the fuel vapors therein, but suflicient. to burn away hot carbonaceous residue from the vaporizing surfaces, and means for supplying liquid hydro carbon fuelalternatively to different of said fuel feeding members.

3. Liquid fuel combustion apparatus for combustion'with'natural draft comprising a burner for continuously burning'a combustible gas mixture, a metal mas's disposed in heatre'eeiving relation with said burner and having a pluralityof vaporizing chambers therein, fuel, feeding members for causing liquid fuel to fall into each of saidchambers to be vaporized by contact with This a hot vaporizing surface therein,.;passages for;. conducting vaporized fwei to' said burner, means for continuously admitting to each of said vapor-- izing chambers a quantity of airinsufilcient to form a combustible gas mixture with the fuel vapors in said chambers but suiflcientto burn away hot carbonaceous residue. from the vapor izing surf'aces, and means for supplying liquid hydrocarbonfuel alternatively to different of said fuel feeding members. t v 4. Liquid fuel vaporizing apparatus forsupplying vaporized hydrocarbon fuel comprising structurefproviding aplurality of vaporizing chambers each having h gh temperature vaporizing sur l facefor vaporizing liquid hydrocarbon fuel, fuel feeding .rnembers for causing liquid fuel to fall on'said vaporizing surfaces, passages for'conducting fuel vapor from said chambers, said? passages being open to permit uninterrupted -fiow' of gaseous fluidfrom said chambers, means for uninterruptedly admitting restricted quantities of. air to said chambers, andmeansfor alternativelysupplyin'g'liquid hydrocarbm fuel to different of said fuel feeding members.

y supplying vaporized hydrocarbon fuel comprising a mass for storing heat, a pluralitylof. vaporizers asso-- ciated with said mass, each of man ow r, 1

eluding a vaporizing chamber, a vaporizing sur- 7 face maintained at a temperature sufllcient to vaporize liquid hydrocarbon fuel by conduction of heat through said mass and a fuel feeding member for causing liquid fuel to fall on said vaporizing surface, passages for continuous withdrawal of gaseous fluid from said vaporizing chambers. means for uninterruptedly admitting restricted quantities of air to said chambers, and means for alternatively supplying liquid fuel to different of said fuel feeding members.

6. Liquid fuel vaporizing apparatus for supplying vaporized hydrocarbon fuel comprising a metal mass heated by a burner and providing a plurality of vaporizing chambers each having a W118 surface heated by conduction of heat from the burner through the mass to a degree Wilt to vaporize liquid hydrocarbon fuel, fuel feeding members for causing liquid fuel to fall on said vaporizing surfaces, passages for uninterrupted withdrawal of gaseous fluid from said vaporizing chambers due to draft created by the burner, meansfor uninterruptedly admitting I?! stricted quantities of air to said vaporizing chambers and means for alternatively supplying fuel to different of said fuel feeding members.

7. Liquid fuel combustion apparatus comprising a burner for burning a gaseous fuel mixture with natural draft, a metal mass in heat receiv ing relation with said burner and providing a plurality of vaporizing chambers each having a vaporizing surface heated by conduction of heat from said burner through the mass to a degree sufmient to vaporize liquid hydrocarbon fuel, fuel feeding members for causing liquid fuel to fall on said vaporizing surfaces, passages for uninterrupted withdrawal of gaseous fluid from said chambers to said burner due to the draft created by combustion in the burner, whereby to supply the burner with fuel vapor for continuous operation, means for admitting quantities of air to the vaporizing chambers insuflicient to form a combustible gas mixture with the vaporized fuel therein but sufficient to burn away carbonaceous residue from said vaporizing surfaces, and means for supplying liquid hydrocarbon fuel alternatively to different of said fuel feeding members.

8. Liquid fuel combustionapparatus comprising a burner for burning a gaseous fuel mixture, liquid fuelvaporizing apparatus comprising two Vaporizers each including a vaporizing chamber, a vaporizing. surface heated by heat from said burner to a temperature sufllcient to vaporize liquid hydrocarbon fuel and a fuel feeding member for causing liquid fuel to fall on said vaporizing surface, passages providing uninterrupted communication between said vaporizing chambers and said burner for supplying fuel vapor to the burner, meansfor uninterruptedly admitting a restricted quantity of air to each of said chambers whereby to retard by combustion the formation of solid carbonaceous deposits therein without forming a combustible gas mixture in the chamber with vaporized fuel therein, and means for alternatively supplying quid hydrocarbon fuel to one or the other of said fuel feeding members.

8. Liquid fuel combustion apparatus comprising a burner for burning a gaseous fuel mixture, means for continuously supplying fuel vapor to the burner comprising a plurality of Vaporizers each including a vaporizing chamber, a vaporizing surface heated by heat from the burner to a degree sufhcient to vaporize liquid hydrocarbon fuel and a liquid fuel feeding member for causing liquid fuel to fall on said vaporizing surface,

for flow to said burner of the passages for flow of gaseous fluid to said burner from said vaporizing chambers, means for uninterruptedly admitting restricted quantities of air to said chambers, and means for supplying liquid hydrocarbon fuel alternatively to different of said fuel feeding members comprising a fuel supply line, 3 S parate fuel supply conduit for each of said fuel feeding members and means for directing fuel from said supply'line to different of said supply conduits.

10. Liquid fuel combustion apparatus comprising a burner for burning a gaseous fuel mixture, means for continuously supplying fuel vapor to the burner comprising a plurality of Vaporizers each including a vaporizing chamber, a vaporizing surface heated by heat from the burner to a degree sufficient to vaporize liquid hydrocarbon fuel and a liquid fuel feeding member for causing liquid fuel to fall on said vaporizing surface, passages for flow of gaseous fluid to said burner from said vaporizing chambers, means for uninterruptedlyadmftting restricted quantities of air to said chambers, and means for supplying liquid fuel alternativelyto diflerentof said fuel feeding members including a common supply line for supplying fuel by gravity, a separate supply conduit leading to each of said fuel feeding members, and switching means for directing fuel from said supply line into different of said supply conduits.

11. The method of producing heat by the aid of a burner, and a plurality of liquid fuel vaporlzers which comprises supplying heat continuously to the Vaporizers from said burner, feeding fuel alternatively to different Vaporizers and forming fuel vapor therein, withdrawing the fuel vapor thus formed due to draft created by the burner, and continuously drawing through the vaporizers a restricted quantity of air whereby to burn away the accumulation of carbonaceous fuel residue in an inactive vaporizer.

12. That improvement in the operation of a liquid fuel vaporizer adapted to supply hydrocarbon fuel vapor intermittently to a burner which consists in heating the vaporizer continuously to a temperature sufiicient to vaporize liquid hydrocarbon fuel. causing liquid fuel to fall on a hot vaporizing surface in the vaporizer for a desired period of time, admitting a restricted quantity of air to the vaporizer while fuel is being yap-- orized therein, whereby to retard the accumulation of carbonaceousfuel residueion said vaporizing surface, and cutting off the supply of fuel to the vaporizer at the end of the desired period of time while continuing the admission of said restricted quantity of air and continuing the heating of the vaporizer after the supply of fuel' to the vaporizer has been cut off, whereby to cause said air to burn away carbonaceous fuel residue from said vaporizing surface during the period when fuel is not admitted to the vaporizer.

13. Apparatus for continuously producing heat comprising a gaseous fuel burner, "a plurality of liquid fuel vaporizers arranged to be continuously heated by heat from said burner, conduit means extending from said burner to said Vaporizers to cause the draft created by the burner to continuously draw a restricted quantity of air through each of the Vaporizers, means for feeding liquid fuel alternatively to different of said vaporizers to form fuel vapor therein for use in said burner, said conduit means including passages vapor formed in any active vaporizer to which fuel is supplied.

14. Apparatus for continuously producing heat comprising a gaseous fuel burner, two liquid fuel Vaporizers arranged to be continuously heated by heat from said burner, means for supplying liquid fuel alternately to one or the other of said Vaporizers to be vaporized therein, conduit means extending from said burner to said Vaporizers so that both of said Vaporizers are continuously subjected to the influence of draft created by said burner and means for continuously admitting a restricted quantity of air to both of said vaporizers, whereby to cause said restricted quantity of air to retard the accumulation of carbonaceous fuel residue in the active vaporizer to which the fuel is being supplied and to burn away such residue in the inactive vaporizer to which fuel is not being supplied.

15. In liquid fuel burning apparatus, a gaseous fuel burner, a liquid fuel vaporizer having a vaporizing surface arranged to be continuously heated by heat from said burner to a temperature suflicient to vaporize liquid hydrocarbon fuel, means for causing liquid hydrocarbon fuel to fall on said vaporizing surface during intermittent spaced time intervals of desired duration to form fuel vapor in said vaporizer during such time intervals, and means for continuously admitting a restricted quantity of air to said vaporizer, whereby to retard the accumulation of carbonaceous fuel residue on said vaporizing surface during the time intervals when fuel is being supplied thereto and to cause said air to burn away from said vaporizing surface during an inactive time interval in which fuel is not supplied to the vaporizer such carbonaceous fuel residue as is formed during an active vaporizing time interval. 16. Apparatus for producing a continuous supply of fuel vapor from liquid hydrocarbon fuel including structure forming different vaporizing chambers each having a vaporizing surface, fuel feeding means for supplying a liquid hydrocarbon fuel alternatively to different ones of said vaporizing surfaces, means for continuously ad'- mitting to each of said vaporizing chambers a quantity of air sufficient to retard by combustion the accumulation of carbonaceous fuel residue on the vaporizing surface therein but insufficient to form in the chamber a combustible mixture with the gaseous hydrocarbon fuel vaporized therein and means for continuously withdrawing gaseous fluid from each of said vaporizing chambers.

17. Apparatus for producing heat comprising a gaseous fuel burner, a plurality of liquid fuel Vaporizers each arranged to be heated continuously by heat from said burner, means for feeding a liquid hydrocarbon fuel alternatively to different ones of said Vaporizers to form fuel vapor therein, conduit means extending from said burner to said Vaporizers to cause draft created'by the burner to draw from said Vaporizers the fuel vapor formed therein, and openings for continuously admitting a restricted quantity of air into each of said Vaporizers, whereby to retard by combustion the accumulation of carbonaceous fuel residue in an active vaporizer to which fuel is being supplied and to burn away such residue in an inactive fuel vaporizer to which fuel is not being supplied.

18. Apparatus for producing heat comprising a gaseous fuel burner, a plurality of liquid fuel Vaporizers arranged to be continuously heated by heat from said burner, conduit means extending from said burner to said Vaporizers to cause draft created by said burner to continuously draw through each of said Vaporizers a quantity of air insufficient to form a combustible gas mixture in any of said Vaporizers with fuel vapor formed therein, and means for feeding liquid hydrocarbon fuel alternatively to different ones of said vaporizers to form fuel vapor therein, said conduit means including passages for flow to the burner of' the fuel vapor formed in any active vaporizer to which fuel is supplied.

19. Liquid fuel combustion apparatus comprising a burner, a plurality 'of Vaporizers for vaporizing liquid fuel for combustion in said burner, means including fuel conduits and fuel flow controlling apparatus for supplying liquid fuel alternatively to different of said Vaporizers and means for continuously admitting a combustion supporting gaseous medium to each of said vaporizers whereby to burn away accumulated carbonaceousfuel residue in said vaporizers during periods of non-supply of liquid fuel thereto.

oos'rAF DALEN. 

